JP5590298B2 - Pressure control device and pressure control method - Google Patents

Description

  The present invention relates to a pressure control that controls a force acting on a pressure receiving body without using a force detector such as a load cell in a machine that operates a working body via a power transmission means by a servo motor to apply a force to the pressure receiving body. The present invention relates to an apparatus and a pressure control method.

Conventionally, as a pressure control device for an electric injection molding machine, a closed loop control unit for injection pressure, a closed loop control unit for injection speed, a disturbance observer calculation unit, a load cell for detecting injection pressure, and an encoder for detecting injection speed The injection pressure closed loop control unit adjusts the operation signal obtained from the pressure set value and the pressure detection value detected by the load cell by the controller, and outputs the injection speed command value. The torque input to the electric motor for the injection shaft is calculated based on the operation signal obtained from the estimated invalid speed estimated by the observer calculation unit, and feedback control is performed so that the pressure of the injection shaft matches the pressure set value. Is known (for example, see Patent Document 1).
However, the load cell has a complicated structure for incorporation into the machine in the injection shaft system from the electric motor to the injection screw, and the detector itself is expensive, and because of the structure for attaching the strain gauge to the detection unit There is a risk of detector failure.

Therefore, in order to avoid problems related to the load cell, it is known that pressure control is performed without using a load cell (force sensor) by configuring an observer that does not require a load cell (for example, Patent Document 2).
Further, the electric injection molding machine requires a step (pressure holding step) of maintaining a predetermined pressure and continuing pressurization after injection and filling the mold. In the pressure holding process, when applying an electric motor so as to maintain a constant pressure, the electric motor may be overloaded. In order to avoid such a problem, an effective load factor of an electric motor (servo motor) is reduced by performing pressure control by superimposing a vibration component on a required target pressure. (For example, refer to Patent Document 3).

JP-A-10-44206 Japanese Patent No. 40222646 JP 2004-114427 A

  However, when the pressure control method described in Patent Document 3 is applied to the control device for the electric injection molding machine of Patent Document 2, a false signal that is not detected by the pressure detected by the load cell is detected by the pressure estimated by the observer. There is a case. In the electric injection molding machine, there is a problem that an estimated pressure value on which such a false signal is superimposed cannot be used as a feedback signal for feedback control.

The present invention has been made in view of the above circumstances, such as an electric injection molding machine, etc., in a machine that operates a working body via a power transmission means by a servo motor and applies a force to a pressure receiving body. An object of the present invention is to provide a pressure control method device and a pressure control method using a servo motor that accurately controls the force acting on the pressure receiving body without using a force detector such as a load cell.
Another object of the present invention is to provide a pressure control device and a pressure control method using a servo motor that can simplify the configuration of the machine and obtain reliability.

The present invention is characterized by the following points in order to solve the above problems.
In other words, a pressure control device using a servo motor according to claim 1 is a machine in which an operating body is operated by a servo motor via a power transmission unit , and a force is applied to the pressure receiving body by the operating body. A pressure control device that controls the force to be applied by controlling the output torque or rotation speed of the servo motor by a control means, and the control means is constructed from a drive unit, a power transmission unit, and an operating body . An observer that is constructed with respect to a control model of the machine and estimates a force received by the operating body based on a current command to the drive unit and rotation information from the drive unit; a current command to the drive unit; A feedback control unit that feedback-controls the force that the operating body acts on the pressure receiving body based on the force estimated by the observer based on the rotation information of the driving unit; Wherein the observer, the drag produced in response to vibration is superimposed as the current command, comprising a composed disturbance observer unit based on the previous SL the control model identified as a disturbance force acting on the actuating body, based on the state quantities output from the disturbance observer unit, so as to reduce the influence of vibration to be superimposed before Symbol current command, and estimates the force acting on the actuating member.

  The pressure control device using the servo motor according to claim 2 is the pressure control device according to claim 1, wherein the disturbance observer unit changes the acting force based on the current command and the rotation information. A state quantity composed of a quantity and a higher-order component of the change amount of the force is estimated.

  A pressure control device using a servo motor according to claim 3 is the pressure control device according to claim 1 or 2, wherein the influence of friction generated in the machine is applied to the current command based on the rotation information. And the observer comprises a change amount of the acting force and a higher-order component of the force change amount based on the compensated current command and the rotation information. The state quantity is estimated.

The pressure control device using the servo motor according to claim 4 is the pressure control device according to any one of claims 1 to 3, wherein the disturbance observer unit superimposes the disturbance as the current command. through the natural frequency of the machine impedance elements of the same frequency as the frequency of the vibration, characterized in that it is constituted on the basis of the control model regarded as acting on the actuating member.

According to a pressure control method using a servomotor according to a fifth aspect of the present invention, in a machine in which an operating body is operated by a servomotor via a power transmission unit and a force is applied to the pressure receiving body by the operating body, the pressure receiving body is operated. the control of the force, said a pressure control method carried out by controlling the output torque or the rotational speed of the servo motor, to build the machine as a control model comprising a drive unit and a power transmission unit operating member and, said control For the model, an observer that estimates the force received by the operating body based on the current command to the drive unit and the rotation information from the drive unit is constructed, and the current command to the drive unit and the rotation information of the drive unit Based on the force estimated by the observer, when the feedback control of the force that the operating body acts on the pressure receiving body, the observer superimposes as the current command. Drag generated according to the vibration, based on the state quantities output from the composed disturbance observer unit based on the control model identified as a disturbance force acting on the front Symbol effector, superimposed before Symbol current command The force acting on the operating body is estimated so as to reduce the influence of vibration.
In the pressure control device and the pressure control method using the servo motor, the machine rotates the ball screw shaft or the ball nut through the pulley and the belt by the servo motor, and the ball nut or An electric injection molding machine that performs molding by operating an injection screw of an injection mechanism via a ball screw shaft and injecting molten resin into a mold clamped by the mold clamping mechanism while controlling the pressure.

The present invention has the following excellent effects.
That is, according to the pressure control device using the servo motor according to claim 1 and the pressure control method according to claim 5, the actuating body is actuated by the servo motor via the power transmission means, and the actuating body serves as the pressure receiving body. In the machine that applies force, the pressure control device that controls the force applied to the pressure receiving body by controlling the output torque or the rotation speed of the servo motor by the control means, the control means includes a drive unit and a power An observer that is constructed with respect to a machine control model constructed from a transmission unit and a driven unit, and that estimates a force received by the driven unit based on a current command to the driving unit and rotation information from the driving unit; The feedback control that feedback-controls the force that the operating body acts on the pressure receiving body based on the force estimated by the observer based on the current command to the driving unit and the rotation information of the driving unit. It comprises a part, a. In addition, the observer includes a disturbance observer unit configured based on a control model in which a drag generated according to vibration superimposed as a current command identifies a force acting on a driven unit via a mechanical impedance element as a disturbance. . The observer can reduce the influence of vibration superimposed on the current command in accordance with the characteristic of the mechanical impedance element based on the state quantity output from the disturbance observer unit, and can estimate the force acting on the driven unit. Therefore, by feedback controlling the operation of the servo motor based on the force, the force that the operating body acts on the pressure receiving body can be accurately controlled without using a force detector such as a load cell.
This eliminates the need for a special means for incorporating the load cell into the machine, thereby simplifying the construction of the machine and improving the reliability of the pressure control device using the servo motor.

It is a block diagram which shows the control apparatus of the electric injection molding machine to which the pressure control apparatus using the servomotor which concerns on one embodiment of this invention is applied. It is a block diagram which shows the structure of an injection pressure setting part. It is a figure shown about the command value of pressure control. It is a figure which shows the control model of this embodiment. It is a block diagram in case a control object is comprised as a two-inertia system control model. It is a figure shown about the control model in this embodiment. It is a figure similarly shown about a control model. Similarly, it is a state variable diagram of the control model. It is the state variable diagram which similarly showed the control model in the other form. It is the state variable diagram of the control model which similarly added the disturbance observer part. It is a figure which shows the repulsion torque (pressure estimated value) of the injection shaft estimated using the observer in the injection control apparatus of this embodiment. It is a figure which shows the estimation result by a general observer system. It is a block diagram which shows the other form which applied the pressure control apparatus using the servomotor which concerns on one embodiment of this invention to the control apparatus which controls the injection pressure of an electric injection molding machine. It is a figure which shows the relationship between a linear friction compensation part and an observer. It is a figure which shows an example of a Coulomb friction compensation characteristic. In the injection control apparatus of this embodiment, it is a figure which shows the result estimated by giving a Coulomb friction compensation to the control command value supplied to an observer. It is a figure which shows the estimation result by a general observer system. It is a figure which shows the estimation result by the observer system of the structure shown in 1st Embodiment. It is a figure which shows the result using the injection control apparatus to which this embodiment is applied.

(First embodiment)
Hereinafter, a pressure control device using a servo motor according to an embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 shows an example in which a pressure control device using a servo motor according to an embodiment of the present invention is applied to a control device for controlling the injection pressure of an electric injection molding machine. In FIG. 1, reference numeral 1 denotes an electric injection molding machine (machine), a heating cylinder 4 having a nozzle 3 at a tip attached to a support plate 2, and a rotation around the axis in the heating cylinder 4 in an axial direction. An injection screw (pressure receiving body) 5 that is movably inserted and a support base 6 that rotatably supports the outer end of the injection screw 5 are provided. The support base 6 is screwed to the ball screw shaft 8 with a pair of ball screw shafts 8 rotatably supported with respect to the support plate 2 and another support plate 7 disposed opposite thereto. It is supported at two locations via a ball nut 9.

  A pulley 10 is attached to one end of each ball screw shaft 8, and a timing belt (belt) 13 is stretched between the pulley 10 and a pulley 12 attached to the output shaft of the servo motor 11. The rotation of the servo motor 11 causes the ball screw shafts 8 to rotate through the timing belt 13 and the pulleys 10 and 12, and the support base 6 reciprocates through the ball nuts 9 screwed into these. As a result, the injection screw 5 moves in the axial direction thereof, and a mold (FIG. 3) is obtained by clamping the molten resin measured at the tip of the heating cylinder 4 by the rotation of the injection screw 5 by a mold clamping mechanism. (Not shown). Reference numeral 14 denotes a pulse encoder (position detector) that generates a pulse corresponding to the rotational position of the servo motor 11.

On the other hand, a control device (control means) 15 for controlling the injection pressure for injecting the molten resin into the mold includes an injection speed setting unit 16 for setting the injection speed set value VSV by the operator, and an injection for setting the injection pressure set value. Servo motor detected by the pressure detector 17 and the rotational angular velocity (rotation information) ω _m (see FIG. 4) derived based on the current rotational position θ of the servo motor 11 detected by the pulse encoder 14 and the current detector 18. 11 is provided with an observer 19 that estimates an injection pressure feedback value from a current value (current command) I for 11 and an injection pressure feedback control unit 20. The injection pressure feedback control unit 20 includes an adder 21 for obtaining a deviation value between the injection pressure feedback value estimated by the observer 19 and the injection pressure setting value by the injection pressure setting unit 17, and performs PID calculation on the deviation value. The first PID calculator 22 to be executed, the comparator 23 for comparing the output value MV of the PID calculator 22 with the injection speed set value VSV by the injection speed setting unit 16, and MV> VSV in the comparator 23 In this case, the PID calculator 22 is composed of a switch 25 for disconnecting the integration element 22a from the circuit.

Further, the control device 15 clamps (limits) the injection speed command unit 26 for obtaining the speed command value SV from the output value MV, and the speed command value SV input from the injection speed command unit 26 by the injection speed set value VSV. ) To output an output value VLIN (VLIN = SV when VSV> SV, VLIN = VSV when VSV ≦ SV), and rotation based on the rotational position θ from the pulse encoder 14. An injection speed feedback input circuit 28 for converting into angular velocity (rotation information) ω _m , and a deviation between the output value VLIN of the injection speed limiter 27 by the adder 29 and the rotation angular velocity ω _m output from the injection speed feedback input circuit 28. An injection speed feedback control unit 31 for obtaining a value and executing a PID calculation by the second PID calculator 30 on the deviation value; and the current detector 18 An adder 32 for calculating a deviation value between the feedback current of the second PID calculator 30 and a calculation output of the second PID calculator 30, and a PID calculator 33 for current control for performing a PID calculation of the deviation value obtained by the adder 32. I have. The output current of the current control PID calculator 33 finally becomes a current command value (current command) I to the servo motor 11. The PID calculators 22 and 30 are variable control constants.

Next, the observer 19 constructs the electric injection molding machine 1 based on a control model composed of a drive unit, a power transmission unit, and a driven unit, an operation command for the drive unit of the control model, and an injection speed It is constructed as an estimator that estimates the force acting on the driven part from the rotational angular velocity (rotation information) of the driving part converted by the feedback input circuit 28. For example, this embodiment shows a two-inertia control model.
That is, the electric injection molding machine 1 of the control model (control model) 38, as shown in FIG. 4, the servo motor 11, through a torque constant element 35a having a torque constant K _t, the summing point 35b The driving unit 35 includes a transmission element including a torque / rotation element 35c coupled to the torque constant element 35a. The torque / rotation element 35c includes a pulse encoder (position detector) 14 and an injection speed feedback input circuit 28, and obtains the rotation angular speed ω _m of the servo motor 11 as an output of the drive unit 35. ,explain.

Further, the control model 38, pulleys 10, 12 and timing belt 13, the respective combined gear ratio to the summing point 35b and the lead point 35d of the driving unit 35 (rotation ratio) pair of rotational angular velocity having a _{R g} Conversion through element 36a, and 36b, and the spring constant element 36c having a spring constant _{K s} of the timing belt 13 coupled with one of the rotational angular velocity conversion element 36a, a summing point 36d while being coupled to the spring constant element 36c The other rotational angular velocity conversion element 36b and the conversion element 36e coupled to the other rotation angular velocity conversion element 36b are configured as a power transmission unit 36.

  In the control model 38, the ball screw shaft 8, the ball nut 9, the support base 6 and the like are coupled to the spring constant element 36c via the addition point 37a and from the lead point 37b to the addition point 36d. It is constructed and constructed as a driven portion 37 composed of a transmission element including a driven element 37c coupled to the conversion element 36e.

Incidentally, the torque / rotary element 35c is configured to include an equivalent moment of inertia of the primary J _m and the viscosity coefficient D _m, the driven element 37c is contained the equivalent moment of inertia of the secondary J _L and the viscosity coefficient D _L It consists of
The observer 19 is supplied with a current command value (current command) I _CMD for the drive unit 35 from a pulling point 35f, and outputs the rotation angular velocity (rotation information) of the servo motor 11 as an output from the drive unit 35. ω _m is supplied from the injection speed feedback input circuit 28, and the estimated value τ _{ext_dc} (hat) of the direct current component of the external force that is the estimated torque (force or pressure) is output.
In addition, the observer 19, the disturbance observer unit 19a for guiding the state variables based on the current command value I _CMD supplied to the observer 19 and the rotational angular velocity omega _m, state variables derived by the disturbance observer unit 19a, i.e. The vibration removing unit 19b is provided for reducing the influence of the disturbance estimated by the disturbance observer unit 19a. A detailed description of the observer 19 will be given later.

A command value for pressure control in the injection control device will be described with reference to FIGS. 2 and 3.
FIG. 2 is a block diagram showing a configuration of the injection pressure setting unit 17.
FIG. 3 is a diagram showing command values for pressure control.
The injection pressure setting unit 17 sets the holding pressure setting values Pi (P1 to P3) at the injection pressure P 1 as constant values that do not change with respect to time t, as shown in FIG. 17a and the constant pressure holding value Pi set in the constant value setting unit 17a are processed, and as shown in FIG. 3B, the pressure fluctuations at a predetermined frequency f (period ω ₀ ) and amplitude A A set value processing unit 17b that outputs a pressure holding command value accompanied by (vibration), a frequency setting unit 17c that sets a frequency f (cycle ω ₀ ) of the pressure holding command value, and an amplitude A of the pressure holding command value An amplitude setting unit 17d for setting the switch, and a changeover switch (switching means) 17e for switching and connecting one of the constant value setting unit 17a and the set value processing unit 17b to the injection pressure feedback control unit 20 I have.
The changeover switch 17e is used to change the setting of whether the servomotor 11 is rotated by a constant pressure holding value Pi from the constant value setting portion 17a or a pressure holding command value Pc from the setting value processing portion 17b. Is to do. The constant value setting unit 17a, the frequency setting unit 17c, and the amplitude setting unit 17d are configured to appropriately input numerical values using a setting key or the like.

  The set value processing unit 17b receives a constant holding pressure set value Pi input from the constant value setting unit 17a as shown in FIG. 3A from the frequency setter 17c and the amplitude setter 17d. The required calculation is performed based on the frequency f and the amplitude A, and as shown in FIG. 3B, the pressure change is repeated as time elapses above and below the constant holding pressure setting value Pi. A holding pressure command value Pc with vibrations consisting of a sin curve, a cosine curve, a triangular wave, a trapezoidal wave, a rectangle and the like having a constant amplitude A and a constant frequency f is processed, and control data corresponding to the holding pressure command value Pc It is stored in the storage area of the injection pressure feedback control unit 20 through the changeover switch 17e.

As a result, the set pressure processing unit 17b displays the holding pressure set value Pi input from the constant value setter 17a based on the frequency f and the amplitude A respectively input from the frequency setter 17c and the amplitude setter 17d. The pressure holding command value Pc accompanied by vibration as shown in 3 (b) is processed. The holding pressure command value Pc is stored in the storage area of the injection pressure feedback control unit 20 through the changeover switch 17e together with the filling pressure set value P0 set by the constant value setter 17a.
For a detailed control method of the pressure control command value in the injection control device, refer to Patent Document 3 and the like.

FIG. 4 is a diagram illustrating a control model of the present embodiment.
In the control model 38 shown in FIG. 4, when the current command value I _CMD is input to the torque constant element 35 a of the driving unit 35 (servo motor 11), the driven unit 37 is operated via the power transmission unit 36. Let As a result, the rotational position θ _m of the drive unit 35 changes and the rotational angular velocity ω _m as an output changes. Then, the observer 19 takes in and the rotational angular velocity omega _m and the current command value _{I CMD.} A deviation between the rotational angular velocity ω _L that should be originally generated by the current command value I _CMD and the captured actual rotational angular velocity ω _m occurs.
The observer 19 estimates the repulsive torque applied to the drive unit 35 based on the deviation of the derived rotational angular velocity. The reaction force against the force received by the driven part 37 from the resistor model 39 (estimated torque (estimated value τ _{ext_dc} (hat)) of the direct current component of the external force) is estimated from the resistance torque. This estimated torque (estimated value τ _{ext_dc} (hat) of the DC component of the external force) is used as an input signal for feedback control of the injection pressure of the electric injection molding machine 1.

FIG. 5 is a configuration diagram when the control target is configured as a two-inertia control model.
First, differential equations relating to the respective state variables when the observer is configured as a two-inertia reaction force estimation observer will be sequentially shown. The variables shown in each equation are as follows: I _CMD is the motor current command value, K _t is the torque constant, R _g is the gear ratio, K _s is the spring constant, J _m is the motor moment of inertia, D _m is the motor viscosity coefficient, J _L There load inertia, D _L is the load side viscosity.

Further, since it can be developed as a state variable diagram 38A as shown in FIG. 8, the rotational angular velocity (rotation information) ω _L on the load side (driven part 37), the servo motor side (driving part 35) and the load side Rotational position difference (rotational angle difference) θ _s , servo motor side rotational angular velocity ω _m , load side torque τ _L received by injection screw 5 from resin pressure (force estimated by observer 19), load side torque τ _L Is represented by τ _L (dot), and the second derivative of the load side torque τ _L is represented by τ _L (two dots). In the equation, τ _L (dot) adds one point (dot) on τ _L. In addition, τ _L (two dots) has two dots (dots) on τ _L respectively.

A differential equation of the torsion angle θ _s , which is a difference in rotational position (rotational angle difference) between the servo motor side (drive unit 35) and the load side, is shown as Expression (1).

The differential equation of the rotational angular velocity (rotation information) ω _{L on} the load side (driven unit 37) is shown as equation (2).

A differential equation of the rotational angular velocity ω _m on the servo motor side (drive unit 35) is shown as equation (3).

FIG. 6 is a diagram showing the definition of disturbance in the present embodiment.
Obtaining a rotational angular velocity omega _m and drives the driven object moment of inertia J _m according to the torque tau _m supplied from the servo motor side shown in FIG. However, the rotational angular velocity ω _m changes with the influence of the load side torque τ _L from the load side with respect to the supplied torque τ _m .
In the present embodiment, the injection screw of an electric injection molding machine 1 (pressure receiving body) 5 (hereinafter, referred to as "injection axis".) Corresponding to the force command value for driving the harmonic component tau _{Ext_ac} of the external force on the DC component tau _{Ext_dc} external force The control is performed so that the static frictional force does not affect the injection shaft of the electric injection molding machine 1. The fundamental frequency of the harmonic component τ _{ext_ac} of the external force is shown as ω ₀ .
The injection shaft of the electric injection molding machine 1 is driven by the command value on which the harmonic component τ _{ext_ac of the} external force is superimposed. When the injection shaft is driven to pressurize the molten resin (injection target), a harmonic component of the reaction force is generated.
Since the harmonic component of the reaction force is generated by the harmonic component τ _{ext_ac} of the external force driven based on the command value, it is generated at the same frequency component, that is, the fundamental frequency ω ₀ .

With a normal observer, if only the harmonic input component superimposed on the input signal is used, the disturbance input can be estimated without being affected by the harmonic. However, in the case of the electric injection molding machine 1, since this disturbance input is a reaction force when the injection shaft pushes the molten resin, the reaction force having the same frequency as the superimposed harmonic force is also a reaction force caused by the injection of the injection shaft. Simultaneously with the force, the electric injection molding machine 1 is applied as a disturbance input.
The harmonic reaction force has the same frequency as the superimposed harmonic, but the molten resin has mechanical impedance, so even with the same frequency reaction force, the phase of the superimposed harmonic force and the phase of the reaction force are different. The phase value is unknown. Therefore, it cannot be modeled because it is impossible to predict what waveform reaction force is applied.
Therefore, the influence of this harmonic component cannot be completely eliminated by an estimation method using a normal observer. Normal observers are both state observers and disturbance observers.

FIG. 7 is a diagram illustrating a control model in the present embodiment.
Therefore, as shown in FIG. 7, the direct current component τ _{ext_dc of the} external force received by the injection shaft passes through the mechanical impedance element 90 having the natural frequency of the same frequency as the harmonic component τ _{ext_ac} of the external force superimposed by the reaction force due to the injection pressure. Thus, a high-order disturbance observer that is not influenced by the natural frequency ω ₀ is configured as the load-side torque τ _L applied to the injection shaft.
In other words, the higher-order disturbance observer, a load-side torque tau _L applied to the injection axis to construct the disturbance observer unit 19a to a disturbance input, including an estimate of the load torque tau _L of the state variable to the estimated output Configure.
Note that the load side torque τ _L acting on the injection shaft varies with the external force τ _ext . As the external force tau _ext includes a DC component tau _{Ext_dc} external force, a sum of the harmonic component tau _{Ext_ac} of the superimposed external forces, represented as formula (4).

This high-order disturbance observer is not affected by the phase of the reaction force of the external force harmonic component τ _{ext_ac} , and the disturbance input (DC component τ _{ext_dc} of the external force) before passing through the mechanical impedance element 90 having the natural frequency. Can be estimated.
As a result, the disturbance input (reaction force) can be estimated without being influenced by the harmonics of the force pressed by the electric injection molding machine 1 and the harmonics received by the molten resin from the environment.

The disturbance observer unit 19a regards an unknown disturbance input as a state variable, adds a state equation, and estimates the disturbance input.
In the injection molding machine modeled by the two-inertia system according to the present embodiment, the load side torque τ _L is affected by the mechanical impedance element 90 and affects the torque τ _m .
Moreover, the differential equation regarding the state variable of the disturbance observer unit 19a is shown as Expression (5).

FIG. 9 is a state variable diagram showing the control model 38 of the electric injection molding machine 1 in another form.
The control model 38B of the electric injection molding machine 1 shown in FIG. 9 can be represented by a state equation expressed as equation (6) and an output equation expressed as equation (7).

In Expressions (6) and (7), A represents a system matrix, B represents a control matrix, x represents a state variable, u represents an input variable, y represents an output variable, and C represents an output matrix. Indicates.
In order to apply the higher-order disturbance observer to the reaction force estimation observer, model parameters are applied and a differential expression of each state variable is derived and expressed as Expression (8).

In the differential equation shown in Equation (8), the rotational speed (rotation information) ω _L on the load side (driven portion 37), the difference in rotational position between the servo motor side (drive portion 35) and the load side (rotation angle) difference) theta _s, rotational speed omega _m of the servo motor _side, load-side torque tau _L of the injection screw 5 receives from the resin pressure (force estimated by the observer _19), a first derivative of the load torque tau _L tau _{L (dots} ) And τ _L (two dots), which is the second derivative of the load side torque τ _L , are given as the state variable x, the state equation is obtained as equation (9) and the output equation is obtained as equation (10).

FIG. 10 is a state variable diagram of a control model in which the control model 38 of the electric injection molding machine 1 is shown in another form and a disturbance observer unit is added.
Based on the configuration shown in FIG. 10, the disturbance observer unit 19 a in the observer 19 can be identified.
Then, based on the state equation shown as the equation (9), for example, a “gopinus design method” is used to design a reaction force estimation observer considering higher-order disturbances.
The designed reaction force estimation observer is shown in Equation (11).

In Expression (11), w represents a converted state variable obtained by converting the state variable, and ζ represents an attenuation coefficient. Moreover, a, b, c, d, and e are shown in Formula (12). However, the _L = 1 / _J L for simplicity of expression.

  Formula (11) is arranged and Formula (13) is obtained as an output of the disturbance observer unit 19a.

In Expression (13), θ _s (hat), ω _L (hat), τ _L (hat), τ _L (dot hat), and τ _L (two dot hat) are state variables estimated by the disturbance observer unit 19a. It is. Estimated values shown in the formula have “^” (hat) on the symbol.
θ _s (hat) is an estimated value of the torsion angle θ _s . ω _L (hat) is an estimated value of the load side rotational angular velocity ω _L. tau _{L (hat),} tau _{L (dots} hat), tau _{L (two-dot} hat), the estimated value of the load side torque tau _L estimated respectively, estimates the first derivative of tau _L, tau _L of the second derivative Is an estimated value.

The external force τ _ext and the load indicated by the control model (see FIG. 6) in which the load side torque τ _L that the DC component τ _{ext_dc of the} external force is influenced by the mechanical impedance element 90 (resonance element) is applied to the control model 38 Based on the relationship of the side torque τ _L , Expression (14) is obtained using τ _L (hat), τ _L (dot hat), and τ _L (two dot hat) derived by Expression (13).

In Expression (14), τ _{ext_dc} (hat) is an estimated value of the DC component τ _{ext_dc} of the external force.
By the procedure shown above, the observer 19 having the disturbance observer unit 19a as an element can be configured.
In addition, it is assumed that the vibration removing unit 19b to which the state variable is supplied from the disturbance observer unit 19a has characteristics opposite to those of the mechanical impedance element 90 described above. The observer 19 _derives an estimated value of the DC component τ _{ext_dc} of the external force.

The effect of this embodiment is shown with reference to FIG. 11 and FIG.
FIG. 11 is a diagram illustrating a repulsion torque (pressure estimation value) of the injection shaft estimated using an observer in the injection control device of the present embodiment.
In this figure, the vertical axis indicates the repulsive torque (pressure estimation value, MPa (megapascal)) of the injection axis, and the horizontal axis indicates the passage of time (seconds).
A waveform G11 is a graph showing the repulsion torque (pressure estimated value) of the injection shaft estimated using the observer. A waveform G12 is a graph showing the pressure detected by the load cell.

From time t1, the injection process is started, and the injection shaft is pushed out in accordance with the control command value _ICMD supplied from the injection pressure setting unit 17. Along with this, the pressure increases monotonously. At time t2, when completing injection of a predetermined amount, injection pressure setting unit 17, the extrusion of the injection shaft is stopped and changed to the control command value I _CMD as the holding pressure step of pressing while maintaining a predetermined pressure. This pressure holding process continues until time t3. When the time t3 has elapsed, the injection pressure setting unit 17 ends the pressure holding process and releases the pressurization state of the pressure holding process. The injection pressure setting unit 17 changes the control command value I _CMD as back pressure step to prepare for the next injection process. In the back pressure process, the molten resin is filled in the heating cylinder 4 while the position of the injection shaft is moved back to the initial position of the next injection process. Since the injection shaft fills the heating tube 4 with the molten resin without unevenness, the injection shaft is maintained at a predetermined pressure and is moved backward while being pressurized so that a negative pressure state does not occur.
In the graph shown in the figure, in the pressure holding process from time t2 to time t3, the pressure detected by the load cell matches the estimated pressure.

Moreover, in order to compare with the effect of this embodiment shown in FIG. 11, the estimation result by the conventional general observer system is shown.
FIG. 12 is a diagram illustrating an estimation result by a general observer method.
In this figure, the result of using a configuration having a control method different from that of the present embodiment is shown, and the command value to be applied is also shown when the harmonic component is superimposed.
A waveform G31 is a repulsion torque (pressure estimation value) of the injection shaft estimated using an observer. A waveform G32 is a pressure detected by the load cell.
In the pressure-holding process from time t2 to time t3, the fluctuation of the same frequency component as the superimposed harmonic occurs in the estimated pressure waveform G31.
Comparing with the result of FIG. 11 according to the present embodiment, it is shown that the error of the estimated pressure oscillation due to the superposition of the harmonic component on the command value can be reduced.

(Second Embodiment)
Hereinafter, a pressure control device using a servo motor according to an embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 13 shows another embodiment in which a pressure control device using a servo motor according to an embodiment of the present invention is applied to a control device for controlling the injection pressure of an electric injection molding machine. The same components as those in FIGS. 1 and 4 are denoted by the same reference numerals.
The electric injection molding machine (machine) 1 shown in FIG. 13 includes a linear friction compensator 40 in addition to the control model 38 and the observer 19 shown in FIG.
The linear friction compensation unit 40 includes a Coulomb friction interpolation unit 41 that performs a Coulomb friction interpolation operation, and a coefficient operator 42 that multiplies the compensation value converted by the Coulomb friction interpolation unit 41 by a predetermined proportional coefficient.
The linear friction compensator 40 reduces the influence of the Coulomb friction when the servo motor 11 is reversed. The linear friction compensator 40 can reduce the influence of the frictional force by interpolating the characteristics in the vicinity of the change point in order to reduce the steep change that occurs at the change point where the rotation direction changes.

FIG. 14 is a diagram illustrating a relationship between the linear friction compensation unit and the observer.
Linear friction compensation unit 40 based on the rotational angular velocity omega _m of the servo motor 11 which is branched from the branch point 35d, generating a compensation amount of the motor torque due to the change in the frictional force. The generated motor torque compensation amount is added to the motor torque by the adder 43. Thereby, the compensated motor torque is supplied to the observer 19.
That is, the control model configured as the observer 19 is not configured to compensate for the Coulomb friction force. However, since the input control command value _ICMD corresponds to the motor torque to be generated, the influence of the static friction force can be reduced by the above compensation method.

FIG. 15 is a diagram illustrating an example of Coulomb friction compensation characteristics.
The graph shown in FIG. 15 shows the conversion characteristics of the Coulomb friction interpolation unit 41.
The vertical axis represents the friction force compensated according to the rotational angular velocity, and the horizontal axis represents the rotational angular velocity.
The range of the motor speed value from −v0 to + v0 is interpolated with the sin characteristic.
A specific interpolation characteristic is shown as Expression (15).

  In equation (15), the setting range of the Coulomb friction interpolation speed v0 can be set in increments of 1 (rotation / minute), for example, from 1 (rotation / minute) to 15 (rotation / minute). In this case, the standard value is 10 (rotations / minute).

With reference to FIG. 16 to FIG. 18, the effect of the present embodiment will be described based on the simulation result.
In this simulation, an experimental value used for the simulation was obtained using a control system configured with a pressure holding vibration of 10 Hz and an observer pole of 70 rad / s. Based on the acquired experimental values (motor torque, motor rotation speed), the configuration of the observer is changed, and the difference in the estimated values by the observers with different configurations is compared. As the parameter of the two-inertia control model to be controlled, the value shown in Expression (16) is used.

FIG. 16 is a diagram illustrating a result of estimation by applying Coulomb friction compensation to a control command value supplied to the observer in the injection control apparatus of the present embodiment.
FIG. 16A is a diagram showing the repulsive torque (estimated pressure value) of the injection shaft estimated by applying Coulomb friction compensation to the command value supplied to the observer in the injection control device of the present embodiment.
In this figure, the vertical axis indicates the repulsive torque (pressure estimation value, MPa (megapascal)) of the injection axis, and the horizontal axis indicates the passage of time (seconds).
A waveform G41 is a graph showing the repulsion torque (pressure estimation value) of the injection shaft estimated by using the observer after performing the Coulomb friction compensation. A waveform G42 is a graph showing the pressure detected by the load cell.

With the configuration of the present embodiment, it is shown that the two waveforms are well matched even in the back pressure process after time t3.
FIG.16 (b) is the figure which expanded and showed a part of Fig.16 (a).
A waveform G51 indicates a part of the waveform G41. A waveform G52 indicates a part of the waveform G42.
The extracted range is 1 second from time 4 seconds to 5 seconds, and corresponds to the pressure holding step (see FIG. 16A).
Comparing the fluctuation of the waveform G51 and the fluctuation of the waveform G52, the waveform G51 is smaller. Moreover, the pressure difference of the average value is about 0.7 (MPa), and even if the average value is compared with the waveform G52 as a reference, it is 102%, and a sufficient value is shown as the estimated value.

Moreover, in order to compare with the effect of this embodiment shown in FIG. 16, the estimation result by the conventional general observer system is shown.
FIG. 17 is a diagram illustrating an estimation result by a general observer method.
FIG. 17A shows the result of comparison using a general observer without performing the Coulomb friction interpolation process.
A waveform G61 is a repulsion torque (pressure estimation value) of the injection shaft estimated using an observer. A waveform G62 is a pressure detected by the load cell.
In the pressure-holding process from time t2 to time t3, the same frequency component variation as the superimposed harmonic is generated in the waveform G61 of the main intended pressure. Also, a difference occurs in the back pressure process after time t3.

FIG. 17B is an enlarged view of a part of FIG.
A waveform G71 indicates a part of the waveform G51. A waveform G72 shows a part of the waveform G52.
The extracted range is 1 second from time 4 seconds to 5 seconds, and corresponds to the pressure holding step (see FIG. 17A).
The amplitude of the vibration component of the estimated pressure indicated by the waveform G71 reaches about 7 (MPa).

FIG. 18 is a diagram illustrating an estimation result by the observer method having the configuration illustrated in the first embodiment. That is, FIG. 18 shows a result of comparison without performing the Coulomb friction interpolation process shown as the second embodiment.
FIG. 18A shows the result of comparison based on the configuration according to the first embodiment.
A waveform G81 is a repulsion torque (pressure estimation value) of the injection shaft estimated using an observer. A waveform G82 is a pressure detected by the load cell.
In the pressure-holding process from time t2 to time t3, the fluctuation of the same frequency component as the superimposed harmonic occurs in the estimated pressure waveform G81. Also, a difference occurs in the back pressure process after time t3.

FIG. 18B is an enlarged view of a part of FIG.
A waveform G91 indicates a part of the waveform G81. A waveform G92 shows a part of the waveform G82.
The extracted range is 1 second from time 4 seconds to 5 seconds, and corresponds to the pressure holding step (see FIG. 18A).
The amplitude of the vibration component indicated by the waveform G91 is about the same as that in FIG. 16B, but the difference between the average values is larger than that in FIG.
As described above, from the results shown in FIGS. 16 to 18, the estimation accuracy is improved by compensating the control command value supplied to the observer 19 shown in the present embodiment in the Coulomb friction compensation process shown in FIG. Can be increased.

Furthermore, with reference to FIG. 19, the result at the time of applying the effect of this embodiment to an actual injection | emission control apparatus is demonstrated.
FIG. 19 is a diagram illustrating a result of using the injection control apparatus to which the present embodiment is applied.
The pressure control method shown as this embodiment was applied to a pressure control device (motion controller) of an actual injection control device (model MD75X manufactured by Niigata Machine Techno Co., Ltd.) for comparison.
FIG. 19A is a graph showing the repulsion torque (estimated pressure value) of the injection shaft estimated using the observer of this embodiment after performing Coulomb friction compensation on the input side of the observer as shown in this embodiment. It is.
In this figure, the vertical axis indicates the repulsive torque (pressure estimation value, MPa (megapascal)) of the injection axis, and the horizontal axis indicates the passage of time (seconds).
A waveform G101 is a graph showing the repulsion torque (pressure estimation value) of the injection shaft estimated by using the observer of the present embodiment after performing Coulomb friction compensation. A waveform G102 is a graph showing the pressure detected by the load cell.
By adopting the configuration of the present embodiment, vibration components in the pressure holding process from time t2 to time t3 are not observed, and in the back pressure process from time t3 to time t4, the two waveforms are highly consistent. It is shown.

In FIG. 19B, as shown in the present embodiment, the Coulomb friction compensation is performed on the input side of the observer. The observer used is the injection shaft resistance torque (pressure) estimated using the conventional observer. It is a graph which shows an estimated value.
In this figure, the vertical axis indicates the repulsive torque (pressure estimation value, MPa (megapascal)) of the injection axis, and the horizontal axis indicates the passage of time (seconds).
A waveform G111 is a graph showing the repulsion torque (pressure estimation value) of the injection shaft estimated by using a conventional observer with Coulomb friction compensation. A waveform G112 is a graph showing the pressure detected by the load cell.

With the configuration of the present embodiment, it is shown that in the back pressure process from time t3 to time t4, the consistency between the two waveforms is high. However, it was observed that a vibration component was generated in the pressure holding process from time t2 to time t3.
As a result, the phenomenon observed in the simulation can be reproduced even when the actual injection control device is used, and the validity of the simulation result using the configuration shown as the present embodiment has been shown.

In addition, the structure shown as embodiment of this invention shows one embodiment, A structure, a capacity | capacitance, a quantity, etc. can be changed in the range which does not change the summary of this invention.
For example, in the present embodiment, the characteristic of the mechanical impedance element 90 that causes a disturbance is shown as a secondary system, but a required order can be selected. In accordance with the order of the selected mechanical impedance element, the order of the load side torque τ _L estimated by the disturbance observer unit 19a is determined together. Further, the characteristic of the vibration removal unit 19b in the subsequent stage is also determined by the mechanical impedance element 90 (resonance system). ) To the opposite characteristic (attenuation system).

In the Coulomb friction compensation shown as means for friction compensation, the interpolation function is shown as a sin function, but other functions that change monotonously (such as polygonal line approximation and trapezoidal interpolation) can be used.
Further, the amount of friction compensation is appropriately determined according to the control system to be applied because it depends on the configuration of the control system to be configured.
Further, the rotation information of the servo motor referred to by the observer can be position information detected as a rotation angle or rotation angular velocity information.

In the above description, the example in which the pressure control device using the servo motor according to the present invention is applied to the case where the injection pressure is controlled by the injection screw in the injection mechanism of the electric injection molding machine 1 has been shown. Not limited to this, it can be applied to control of the back pressure applied to the injection screw during weighing, or the movable plate can be moved directly or indirectly via a linear movement mechanism in which a ball nut is screwed onto the ball screw shaft by a servo motor. The present invention can also be applied to the case of controlling the mold clamping pressure in the mold clamping mechanism for clamping the mold between the movable platen and the fixed platen, or the case of controlling the ejecting pressure of the ejector.
Furthermore, the linear movement mechanism formed by screwing the nut onto the screw shaft via the transmission mechanism by the electric motor is operated, and the pressure plate connected to the linear movement mechanism is moved, and the pressure plate and the fixed plate are moved. In a press machine that press-molds a workpiece in between, the pressure (force) applied to the pressure platen can be controlled, and the pressure (force) can be controlled in other industrial machines.

In addition, in the machine which operates an operating body via the power transmission means by the servo motor 11 of the present embodiment and applies force to the injection screw 5 (pressure receiving body) by the operating body, control of the force applied to the injection screw 5 is controlled. Is a pressure control device that controls the output torque or the rotational speed of the servo motor 11 by the control means, and the control means 15 controls the machine constructed by the drive unit, the power transmission unit, and the driven unit. An observer 19 that is constructed for the model and estimates the force received by the driven unit based on the current command to the driving unit and the rotation information from the driving unit, and the current command to the driving unit and the rotation of the driving unit A feedback control unit that feedback-controls the force that the operating body acts on the pressure-receiving body based on the force estimated by the observer 19 based on the information. The observer 19 is configured based on a control model in which the drag generated in response to the vibration superimposed as the current command value I _CMD identifies the force acting on the driven part via the mechanical impedance element 90 as a disturbance. Based on the disturbance observer unit 19a and the state quantity output from the disturbance observer unit 19a, the influence of vibration superimposed on the current command is reduced according to the characteristics of the mechanical impedance element 90, and acts on the driven unit (37). Estimate force.
Thereby, the characteristic of the disturbance observer part 19a can be determined easily.

Further, the disturbance observer unit 19a of the present embodiment estimates a state quantity composed of a change amount of the acting force and a higher-order component of the change quantity of the force based on the current command and the rotation information.
Thereby, the change amount of the acting force can be estimated up to higher order components, and the influence can be reduced from the estimated information.

Further, based on the rotation information of the present embodiment, a friction compensation unit that compensates the current command for the influence of friction generated in the machine (1) is provided, and the observer 19 includes the compensated current command, the rotation information, Based on the above, a state quantity consisting of a change amount of the acting force and a higher order component of the acting force change amount is estimated.
Thereby, the change amount of the acting force can be estimated up to higher order components, and the influence can be reduced from the estimated information.

In addition, the disturbance observer unit 19a of the present embodiment has a control model that considers the disturbance to act on the driven unit (37) via the mechanical impedance element 90 having the natural frequency of the same frequency as the vibration superimposed as the current command. Configured based on.
Thereby, the influence of the vibration superimposed on the current command (control command value) easily detected as a disturbance from the state variable estimated by the disturbance observer unit 19a can be easily reduced.

1 Electric injection molding machine (machine)
4 Heating cylinder 5 Injection screw (pressure receiving body)
6 Support base 8 Ball screw shaft 9 Ball nut 10, 12 Pulley 13 Timing belt (belt)
14 Pulse encoder (position detector)
DESCRIPTION OF SYMBOLS 15 Control apparatus 16 Injection speed setting part 17 Injection pressure setting part 18 Current detector 19 Observer 20 Injection pressure feedback control part

Claims (5)

In a machine in which an operating body is operated by a servo motor via a power transmission unit and a force is applied to the pressure receiving body by the operating body, the force applied to the pressure receiving body is controlled by the control means by the output torque of the servo motor or A pressure control device that controls the rotational speed,
The control means is constructed with respect to a control model of the machine constructed from a drive unit, a power transmission unit, and an operating body , and based on a current command to the drive unit and rotation information from the drive unit. An observer for estimating the force received by the operating body ;
A feedback control unit that feedback-controls the force that the operating body acts on the pressure receiving body, based on the force estimated by the observer based on the current command to the driving unit and the rotation information of the driving unit;
With
The observer is
Drag generated in response to vibration is superimposed as the current command, comprising a composed disturbance observer unit based on the previous SL the control model identified as a disturbance force acting on the actuating body,
Use based on the state quantities output from the disturbance observer unit, so as to reduce the influence of vibration to be superimposed before Symbol current command, the servo motor and estimates the force acting on said actuating member Had pressure control device. The disturbance observer unit is
2. The servo according to claim 1, wherein a state quantity composed of a change amount of the acting force and a higher-order component of the change quantity of the force is estimated based on the current command and the rotation information. Pressure control device using a motor. A friction compensation unit that compensates for the current command with respect to the influence of friction generated in the machine based on the rotation information,
The observer is
The state quantity consisting of a change amount of the acting force and a higher-order component of the change quantity of the force is estimated based on the compensated current command and the rotation information. Alternatively, a pressure control device using the servo motor according to claim 2. The disturbance observer unit is
The disturbance, characterized in that constructed on the basis of the control model regarded as acting on the actuating body via the natural frequency of the machine impedance elements of the same frequency as the frequency of vibration is superimposed as the current command The pressure control apparatus using the servomotor in any one of Claims 1-3. In a machine in which an operating body is operated by a servo motor through a power transmission unit and a force is applied to the pressure receiving body by the operating body, the force applied to the pressure receiving body is controlled by controlling the output torque or the rotational speed of the servo motor. A pressure control method performed by controlling,
The machine is constructed as a control model including a drive unit, a power transmission unit, and an operating body, and the operating body is configured based on a current command to the driving unit and rotation information from the driving unit. Build an observer to estimate the force
Based on the force estimated by the observer based on the current command to the drive unit and the rotation information of the drive unit, when feedback controlling the force that the operating body acts on the pressure receiving body,
The observer is
Drag generated in response to vibration is superimposed as the current command, based on the state quantities output from the composed disturbance observer unit based on the control model identified as a disturbance force acting on the front Symbol effector, so as to reduce the influence of vibration to be superimposed before Symbol current command, a pressure control method using a servo motor and estimates the force acting on the actuating member.

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